In the 3rd Generation Partnership Project (3GPP) as a standardization project, the Evolved Universal Terrestrial Radio Access (hereinafter referred to as EUTRA) that has realized high-speed communication has been standardized by employment of orthogonal frequency-division multiplexing (OFDM) communication scheme and flexible scheduling by prescribed frequency and time units that are referred to as resource block.
Further, the 3GPP has realized further high-speed data transmission and has been discussing Advanced EUTRA that is upper compatible with EUTRA. As for EUTRA, a communication system is based on a network in which base station devices are formed in almost the same cell configuration (cell size). However, as for Advanced EUTRA, a communication system has been discussed, which is based on a network (heterogeneous network) in which base station devices (cells) with different configurations are intermingled in the same area.
In a communication system as the heterogeneous network in which cells with a large cell radius (macrocell) and cells with a smaller cell radius than the macrocell (small cell) are arranged, a dual connectivity technique has been discussed, in which a terminal device simultaneously connects with the macrocell and the small cell and performs communication (NPL 1).
NPL 1 discusses a network on the presupposition that backbone lines (backhaul) between the macrocell and the small cell are at a low speed and delay occurs when the terminal device attempts to realize the dual connectivity between the cell with a large cell radius (cell size) (macrocell) and a cell with a small cell radius (small cell (or picocell)). That is, it may become unfeasible or difficult to realize functions that are realized in related art due to delay of interchange of control information or user information between the macrocell and the small cell.
Further, NPL 2 discloses a method of feeding back channel state information in the cell when the terminal device simultaneously connects with plural cells that are coupled together by high-speed backhaul.